Flox

After coming across PostHog’s Isolated Development with Flox, I wanted to see how to compared to devbox, my go-to for managing my development environment.

TL;DR

Flox, like devenv and devbox is a nix-wrapper for managing development environments. Devbox feels akin to npm install, but for binaries. I recommend using it instead of Flox.

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Installation

Don’t use brew install flox. It installs a Cask that’s failed to even run.

Instead, download the installer.

Setup

In my project, I started with a simple:

flox init

This craetes a .flox root directory, just like devbox does for .devbox.d.

Since packages come from nix, setting up Node.js was as easy as:

flex search nodejs
flex install nodejs_24

Finally, I needed to activate the shell:

flox activate

Going Further

It’s easy to forget to activate the shell when switching between projects.

I learned about direnv previously whose utility is primarily auto-activating the shell when entering a project directory.

Flox’s blog has a guide titled Auto Environment Activation with Direnv + Flox that’s essentially:

echo 'eval "$(flox activate)"' > .envrc && direnv allow

Stopping Point

So far, my experience hasn’t been great:

1. brew install flox is just a Cask for the installer that’s buggy.

   I recommend removing that entirely to avoid the indrection and operational burden of supporting a wrapper.

2. Layered environments aren’t straightforward to use.

Just having direnv auto-activate wasn’t clear enough, even with this article. There are documented issues with the PS1 prompt disappearing (which is admittedly more of a direnv issue).

But the biggest turn-off was running flox edit to manage a manifest.toml file.

Devbox, at least, will update devbox.json for you automatically.